boards/serpente: add SAUL PWM integration

boards/serpente/Makefile.dep

@@ -3,7 +3,7 @@ ifneq (,$(filter mtd,$(USEMODULE)))
 endif
 
 ifneq (,$(filter saul_default,$(USEMODULE)))
-  USEMODULE += saul_gpio
+  USEMODULE += saul_pwm
 endif
 
 # setup the samd21 arduino bootloader related dependencies

boards/serpente/include/pwm_params.h

@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2020 Marian Buschsieweke
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     boards_serpente
+ * @{
+ *
+ * @file
+ * @brief       Configuration of SAUL mapped PWM channels
+ *
+ * @author      Marian Buschsieweke <marian.buschsieweke@ovgu.de>
+ */
+
+#ifndef PWM_PARAMS_H
+#define PWM_PARAMS_H
+
+#include "board.h"
+#include "saul/periph.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static const saul_pwm_rgb_params_t saul_pwm_rgb_params[] =
+{
+    {
+        .name  = "LED",
+        .channels = {
+            { PWM_DEV(0), 3, SAUL_PWM_INVERTED },
+            { PWM_DEV(0), 2, SAUL_PWM_INVERTED },
+            { PWM_DEV(0), 4, SAUL_PWM_INVERTED }
+        }
+    }
+};
+
+#define SAUL_PWM_NO_DIMMER
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* PWM_PARAMS_H */
+/** @} */